Children with inherited diseases, characterized by impaired primary deposition of elastic fibers (i.e. Costello Syndrome or Cutis Laxa) develop wrinkles and deep dermal creases. Similar, but steadily developing signs of premature skin aging can also be observed in individuals with Pseudoxanthoma Elasticum and in normal persons after prolonged exposure to sun. Histological analysis of wrinkled skin demonstrates disappearance and altered organization of elastic fibers due to premature proteolytic degradation and impaired remodeling (solar elastosis) of these components of dermal extracellular matrix. This observed loss of physiologically relevant elastic fibers is also affected by the fact that fully differentiated (adult) dermal fibroblasts lose their ability to synthesize elastin and thus cannot replace damaged elastic fibers. Since elastic fibers are solely responsible for cutaneous elasticity/resilience there is an obvious need for development of methods that might protect existing elastic fibers from premature degradation by elastolytic proteinases and facilitate new elastogenesis in skin.
A proteolytic digest of elastin to provide a mixture of small elastin-derived peptides (ProK-60), manganese salts (MnCl2, MnSO4 and MnPCA) and trivalent iron (Ferric Ammonium Citrate) have each been shown to individually stimulate the production and effective assembly of new tropoelastin into new elastic fibers in both primary cultures of human dermal fibroblasts and in organ cultures of human adult skin explants. Yet even under optimal conditions, the elastogenic process is not 100% efficient. A significant fraction (30-40%) of newly produced tropoelastin is not assembled into extracellular elastic fibers. Instead, these unassembled tropoelastin interact with the cell surface elastin receptor and further stimulate new elastogenesis, pro-mitogenic signaling pathways and pro-migratory signaling pathways. Moreover, these unassembled tropoelastin molecules and the soluble products of proteolytic degradation of insoluble elastin can stimulate the secretion of elastolytic metalloproteinases. While stimulation of dermal fibroblast proliferation and migration can contribute to the overall anti-aging effect induced by factors initially triggering new elastogenesis, the simultaneous up-regulation of elastolytic enzymes may cause rapid degradation of newly produced elastin and existing elastic fibers. Hence there is a need to protect existing and new elastic fibers from premature enzymatic proteolysis.
It has now been shown that the treatment of cultured dermal fibroblasts with ellagic acid or tannic acid significantly enhances their net deposition of elastic fibers. This effect is due to the fact that these reagents bind to the newly produced elastin and protect it from proteolytic degradation.
Ellagic acid and tannic acid are polyphenols found in a wide variety of fruits and nuts such as raspberries, strawberries, walnuts, grapes, and black currants. These molecules possess potent ability to scavenge reactive oxygen species (ROS) and reactive nitrogen species (RNS). Both ROS and RNS, generated inside cells after exposure to several endogenous and exogenous agents, may cause direct or indirect damage of many important biomolecules, including elastin mRNA, by activation of local proteinases, glycosidases or RNAses. Moreover, tannic acid has been shown to bind to insoluble bovine and porcine elastin and inhibit their degradation by porcine pancreatic elastase and recently, ellagic acid was shown to decrease expression of pro-MMP-2 and pro-MMP-9, precursors of two elastolytic enzymes.
The most extensively studied polyphenol, ellagic acid, exhibits minimal solubility in water and moderate to better solubility in organic solvents such as methanol and DMSO, suggesting that ellagic acid may act as a good lipophilic antioxidant. Experimental data indicate that ellagic acid inhibits lipid peroxidation at much lower concentrations than vitamin E. This property, along with its ability to scavenge peroxyl radicals, makes it a probable chain-breaking antioxidant candidate.
Epidemiological studies indicate that there is an inverse association between the incidence of coronary heart diseases and fruit consumption, largely attributed to the antioxidant nature of phenolic compounds. Ellagic acid exhibits cardio-protective properties in the neoepinephrine myocarditis rat model, hepato-protective activity against carbon tetrachloride both in vitro and in vivo and reduced cytogenetic damage induced by radiation, hydrogen peroxide and mitomycin C.
Additional experimental studies have demonstrated that ellagic acid, tannic acid and their derivatives, due to their planar structure, also bind to DNA by intercalating into the minor groove and exhibit anti-mutagenic, anti-cancer and anti-proliferative activities. In addition, ellagic acid induces G1 arrest and inhibits overall cell growth, causing apoptosis in several tumor cells. Ellagic acid has also been shown to inhibit chemically induced cancer in the lung, liver, skin and esophagus of rodents, including TPA-induced tumor promotion in mouse skin. Given the common etiopathogenic processes of mutagenesis, carcinogenesis, and teratogenesis induced by genotoxic chemicals, ellagic acid was also tested for embryoprotection and demonstrated that it can interrupt the critical teratogenic events induced by methylating agents.
Topical applications of ellagic acid have been used in therapeutic preparations. Gali, et. al. demonstrated that topical applications of tannic acid practically inhibit tumor promoter-induced ornithine decarboxylase activity (ODA) in mouse epidermis in vivo suggesting that tannic acid and other polyphenols may be effective not only against skin tumor initiation and complete carcinogenesis, but also against the promotion phase of skin tumorigenesis. Moreover, tannic acid and its polyphenol derivatives have been shown to possess anti-inflammatory activities and to decrease infectivity of human cells with papiloma virus, human immunodeficiency virus, and Staphylococcus aureus. 